The present invention relates generally to an image recording apparatus, and more particularly to an exposure device incorporated in an image recording apparatus, such as a copying machine, facsimile equipment or the like.
U.S. Pat. No. 4,399,209 to Sanders et al discloses a photosensitive pressure-sensitive recording medium having a surface coated with an immense number of photo-curable microcapsules encapsulating a chromogenic material therein. For the recordation of an image, the recording medium is exposed to an imaging light to selectively photocure the microcapsules and to thus form a latent image thereon. Thereafter, the recording medium and a separate image receiving sheet having a surface coated with a developer material are brought to facial contact with each other and are subjected to pressure development to rupture the microcapsules which remain uncured and to react the chromogenic material released from the ruptured microcapsules with the developer material. As a result, a visible image is formed and transferred onto the image receiving sheet.
In the photosensitive pressure-sensitive recording media of the type described above, it has been known that the photosensitivity thereof varies depending upon ambient temperature and/or humidity. Due to the fact that the ambient temperature and/or humidity usually vary depending upon weather, time, etc, the image recording is not always performed under the most suitable condition and thus the quality of the image as reproduced cannot be maintained at a constant level. Even if both the temperature and humidity were maintained unchanged, the ambient temperature and humidity would vary due to the heat generated from an exposure lamp, thereby causing to vary the photosensitivity of the recording medium. Therefore, the same level image quality cannot be constantly obtained even if the temperature and the humidity were set to predetermined constants and the same amount of light were applied onto the recording medium for exposure.
Furthermore, although the image receiving sheet is substantially not affected by temperature and humidity, the image transfer to the image receiving sheet is degraded as the ambient humidity exceeds about 70%, and the developer material coated on the surface of the image receiving sheet is liable to be peeled off as the ambient temperature raises above about 40 centigrade. In addition, with respect to an image receiving sheet using a transparent film as the substrate material, which is used in an overhead projector, the image formed thereon is light in density as compared with the image formed on an image receiving sheet whose substrate material is a paper.